of entertaining metaphysical motives. Wundt will not admit any causal connection between the physical and psychical series; each seems to flow on regardless of the other, but somehow bound to take notice of the other after the fashion of a preestablished harmony.[1] His article, 'Ueber psychische Causalität,' etc.,[2] is a polemic against what he calls the materialistic psychology, in which a causal relation is assumed between physical states and states of consciousness. I really see no reason why one should not be frankly and outspokenly materialistic in a natural science. It is understood that the question about ultimate reality is not raised at all, and until this question is raised there is no metaphysic.
But it certainly comes to the same thing in science to say that a physical state is the universal antecedent, or the universal concomitant, or the cause of a given mental state. When consciousness is disordered because of an observable accident to the brain, one says the condition of the brain thus introduced is the cause of the disordered consciousness. There seems no more purpose in speaking of it as a merely parallel physical state which is, however, not a cause of a mental state, than to speak of a stroke of apoplexy and the bursting of a blood-vessel as parallel physical states, but not to be taken as causes of changes in consciousness. Epistemology and the higher criticism of concepts may ask in what sense the word 'cause' is here used, but if the psychologist can say that without the physical state, the mental state would not have occurred, he has enough ground for using the word 'cause' in a frank and practical way. But in doing so he will be raising no question about reality, he will simply be assuming that his phenomena are explainable by causal relations.
Thus the relations which the psychophysical point of view assumes are relations for the purpose of explanation, but it is an explanation within the limits of phenomena, and no metaphysical implications are permitted. The explanation is not an ultimate explanation; the triumph of the point of view would be to be brought around again into the mental series, to be able to predict the mental states from the physical ones. That is, the triumph would lie not in an explanation, but in a description, and this hope, this possibility it is which makes explanations important parts of scientific undertakings. The explanation which confessedly is no help to a new observation may be interesting, but it hardly seems important. And if it helps to a new observation it fulfills its function, whatever its concepts may be. There may indeed be a metaphysical concept of psychophysical parallelism, such a doctrine as that of Spinoza, for
